1. Field Of The Invention
This invention relates to an electronic circuit for monitoring load imbalances between the two phases of a 110/220 electrical service, and more particularly relates to a circuit which maintains optimum balance between the two phases, either by transferring or shedding loads, thereby reducing the consumption component of the electric bill.
2. Description Of The Related Art
U.S. Pat. No. 3,987,308 entitled "Peak Load Control Energy Saving And Cycling System", issued Oct. 19, 1976 to Burch, is directed to a control system which adds or drops loads to limit peak loads. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,153,936 entitled "Energy Management System", issued May 8, 1979 to Schmitz, is directed to a system which energizes and deenergizes loads in response to preselected conditions and time frames. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,245,319 entitled "Energy Management Method And Apparatus Utilizing Duty Cycle Reduction Synchronized With The Zero Points Of The Applied Voltage", issued Jan. 13, 1981 to Hedges, is directed to apparatus which automatically sheds certain loads when the actual demand of the circuit exceeds the demand limit. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,321,477 entitled "Energy Management Apparatus And Method", issued Mar. 23, 1982 to Bartlett, is directed to a system which controls the power to a plurality of loads while limiting peak demands. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,345,162 entitled "Method And Apparatus For Power Load Shedding", issued Aug. 17, 1982 to Hammer, is directed to apparatus for load shedding duty cycling. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,347,576 entitled Load Management Control Apparatus With Improved Duty Cycle Operation", issued Aug. 31, 1982 to Kensinger, is directed to duty cycle apparatus. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,612,619 entitled "Energy Management Load Leveling", issued Sep. 16, 1986 to Culp, is directed to a load cycling system. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,659,943 entitled "Peak Demand Limiter", issued Apr. 21, 1987 to Virant, is directed to a peak demand limiter used to detect and limit by selective activation the peak load or demand of a circuit. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
U.S. Pat. No. 4,694,192 entitled "Simplified Demand Limit Control", issued Sep. 15, 1987 to Payne, is directed to a demand limit control system which sheds loads to limit demand. This reference does not teach transferring a load from one phase to another to balance the current draw between the phases.
Chapter 7 of the "Handbook for Electricity Metering" 8th Ed., published by the Edison Electric Institute, 1111 19th Street N.W., Washington D.C. 20036 (ISBN 0-931032-11-3), teaches that multi-stator meters will register a lower value if the stators are equally loaded than if the stators are not equally loaded. This reference does not teach or suggest a combination of transferring and/or shedding loads between the two phases to optimally balance the loads and thereby register a lower reading.
All of the above mentioned references take advantage of the fact that by limiting the demand to a certain level, energy costs can be reduced. They accomplish this by a variety of methods including peak demand limiting, load shedding and duty cycling. However, none of these reference teach or suggest the advantage of combining these methods with load balancing between the phases of the electrical service.